Vaccines are one of the most controversial topics among parents these days, with a growing number questioning whether to give their kids recommended shots.

Nearly 40% of parents have delayed or declined at least one of their children's shots — a practice that's fueling outbreaks of infectious diseases, from mumps to measles and whooping cough, that were once nearly eliminated by vaccination, according to the Centers for Disease Control and Prevention.

Yet much of the anxiety about vaccines is based on myths and fear, rather than facts.